OPC-UA Client: Support for ExtensionObjects

[Jayclifford345]

Feature Request

In more complex OPC-UA server architectures there is heavy use of extension objects. An ExtensionObject is a container for any Structured DataTypes which cannot be encoded as one of the other built-in data types. A prime example for this would be an alert:

struct custom_alert {
    bool    door_open;
    int32_t current_operating_mode;
    float   temperature;
};

Proposal:

We should provide functionality within the OPC-UA client for deserializing Extention Objects. This could be done by pre-declaring Extention Objects to the client. I believe gopcua does support an Extention Object repository though I do not know if these objects need to be declared before the binary is built.

[vdkost]

thank you for opening the request. I search for a possibility to handle more complex ExtensionObjects with customized dataTypes, like BooleanCollection

or FloatCollection

[quenorha]

I would also add the array object support as feature request, since using arrays can really lower the CPU load of the server for same number of data.

[magiconair]

https://github.com/gopcua/opcua does support extension objects but they have to be declared and registered at compile time. See https://github.com/gopcua/opcua/blob/main/examples/udt/udt.go

I'm open for a dynamic definition of extension objects at runtime and then discovery through the type dictionary. PRs are welcome.

[Daniel-Deimann]

What is the expected date that this will be implemented ? Or is there a work-around for the time being?